Opinion on PCV valve for flathead?
- Thread starter BobM
- Start date
santino2010
Member
hello there im trying to also run pcv on my 239 flatty but im using stock intake manifold.
can anyone send me more specific photos of how to do this step by step thank you
can anyone send me more specific photos of how to do this step by step thank you
santino2010
Member
Yes but I would like to see how to modify my intake manifold if anyone has pictures that would be helpful thanks
Fourdy
Well-known member
Hey Mart, you have to work a lot harder than that to cause me any grief. LOL I don't have a road draft tube. The manifold is one of the goofy offy type that wasn't bored for the draft tube. I called offy and was told it just saved money to use one blank for both styles.
Fourdy
Fourdy
V8 Bob
Well-known member
I think there may be some confusion on early and late flathead ventilation.
On the '35-'48s, air enters at the rear, moves down into the crank case, up into the valve chest and then down the vertical tube which leads directly to the pan (road draft) vent.
On the 8BA, air enters at the front, moves through the valve chest and down into the crank case, then up through the vertical tube and into the road draft pipe through the intake.
JSeery
Member Emeritus
I think there may be some confusion on early and late flathead ventilation.
On the '35-'48s, air enters at the rear, moves down into the crank case, up into the valve chest and then down the vertical tube which leads directly to the pan (road draft) vent.
On the 8BA, air enters at the front, moves through the valve chest and down into the crank case, then up through the vertical tube and into the road draft pipe through the intake.
Ok, but not sure with a PVC why you can't vent off of about anywhere. You are releasing crankcase pressure and exhausting blow by. Not sure it is important to follow a specific path, although good circulation would help. How was Ford's PCV system setup, that might be a good example?
Edit: On second thought that is not going to help much! Ford's PCV would have been in the war years and a 59a style block.
Last edited:
Fourdy
Well-known member
I guess I'm thinking that fresh air in through the oil fill, thru the valley into the pan then forward to the capped stand pipe in the valley, thru the tube to pcv then to manifold vacuum to help burn some of the bad stuff all up. Always ready to learn.
Never THE WAY, just the way I did it.
Fourdy
Never THE WAY, just the way I did it.
Fourdy
V8 Bob
Well-known member
Ford installed a pcv in the intake manifold near the area of the front stand pipe, pulling the fumes up and then plumbed to the carb base (manifold vacuum), instead of allowing them to exit down the stand pipe and out the pan vent, according to pictures I've seen of WW11 military flatheads.
JSeery
Member Emeritus
I thought I had an article on that whole set up somewhere, but I can't find it!
blucar
Well-known member
From my prospective, based on many applications of PCV systems on pre "SMOG" engines that I have done, I have formed the opinion that very few people really have a clear grasp on how a Positive Crankcase Valve system works.
The object of a PCV system is to draw clean, filtered air into the engine, circulated it through the engine, utilizing engine vacuum, then introduce the oil contaminated air into the intake system where it is blended with the air/fuel mixture and is burned off.
The introduction of the PCV system in 1963, eliminate 90% of the "SMOG" vapors that the internal combustion engines emitted via the open road draft devise (s) that had been in use since the invention of the internal combustion engine.
Many years ago I encountered the PCV system that Ford used on the '64 Y-Blocks. This system used a little dome shaped cap that replaced the '63 and earlier road draft tubes, the cap had a fitting for a 3/8" hose, the hose was attached to a PCV that was threaded into the intake manifold.
Air was drawn into the crankcase via the filtered oil fill cap, the vacuum then pulled the air flow through the block/valve chamber and into the intake manifold, to be burned off.. No blow by, no crankcase pressure, just a well ventilated clean engine.
GM used a variation of the same domed adapter to eliminate the road draft tubes on the '63 SBC's, the only difference was GM used a PCV that plugged into a valve cover via a rubber grommet.
Some Y-Blocks have a crankcase breather on the lower left side of the block, this could be compared to the pan breather on the left side of many of the early flathead engine.. The block/pan breather has to be blocked off in order for a PCV to work properly.
OK now the problem is, how do you utilize a simple system like the Y-Blocks? Very simple, don't try to reinvent the wheel, and don't over engineer the system.
The 8BA/8CM engines are the easiest, eliminate the road draft tube from the front of the engine, fabricate something to take it's place to which a 3/8" hose can be attached. Find a good vacuum source, below the throttle plate (s).. Use a PCV that is from an engine that is close to the CID of the engine being modified.
From my way of thinking the system would work best if the air was drawn in from the rear of the engine, maybe via a modified early V8 modified fuel pump stand with a filtered cap on top.
I would think that if the vacuum is pulling vapors from the block via the old road draft port, and the original oil fill pipe was left open, circulation of the vapors would not be good.. Ya know the shortest distance between two points..
The early flatheads are more of a challenge because of the intake manifold would require drilling and threading of a hole that the PCV could be threaded into, then a vacuum source has to be obtained..
The WWII military vehicles used a closed crankcase, i.e. PCV because many of them were equipped to keep water out of the engine, because they "forded" water deeper than the engines, the breathers were extended to above the windshield, and/or they were intended for desert use in extremely dusty conditions...
The object of a PCV system is to draw clean, filtered air into the engine, circulated it through the engine, utilizing engine vacuum, then introduce the oil contaminated air into the intake system where it is blended with the air/fuel mixture and is burned off.
The introduction of the PCV system in 1963, eliminate 90% of the "SMOG" vapors that the internal combustion engines emitted via the open road draft devise (s) that had been in use since the invention of the internal combustion engine.
Many years ago I encountered the PCV system that Ford used on the '64 Y-Blocks. This system used a little dome shaped cap that replaced the '63 and earlier road draft tubes, the cap had a fitting for a 3/8" hose, the hose was attached to a PCV that was threaded into the intake manifold.
Air was drawn into the crankcase via the filtered oil fill cap, the vacuum then pulled the air flow through the block/valve chamber and into the intake manifold, to be burned off.. No blow by, no crankcase pressure, just a well ventilated clean engine.
GM used a variation of the same domed adapter to eliminate the road draft tubes on the '63 SBC's, the only difference was GM used a PCV that plugged into a valve cover via a rubber grommet.
Some Y-Blocks have a crankcase breather on the lower left side of the block, this could be compared to the pan breather on the left side of many of the early flathead engine.. The block/pan breather has to be blocked off in order for a PCV to work properly.
OK now the problem is, how do you utilize a simple system like the Y-Blocks? Very simple, don't try to reinvent the wheel, and don't over engineer the system.
The 8BA/8CM engines are the easiest, eliminate the road draft tube from the front of the engine, fabricate something to take it's place to which a 3/8" hose can be attached. Find a good vacuum source, below the throttle plate (s).. Use a PCV that is from an engine that is close to the CID of the engine being modified.
From my way of thinking the system would work best if the air was drawn in from the rear of the engine, maybe via a modified early V8 modified fuel pump stand with a filtered cap on top.
I would think that if the vacuum is pulling vapors from the block via the old road draft port, and the original oil fill pipe was left open, circulation of the vapors would not be good.. Ya know the shortest distance between two points..
The early flatheads are more of a challenge because of the intake manifold would require drilling and threading of a hole that the PCV could be threaded into, then a vacuum source has to be obtained..
The WWII military vehicles used a closed crankcase, i.e. PCV because many of them were equipped to keep water out of the engine, because they "forded" water deeper than the engines, the breathers were extended to above the windshield, and/or they were intended for desert use in extremely dusty conditions...
Attachments
V8 Bob
Well-known member
The 8BA intake gasket isolates and directs the vertical stand pipe directly to the road draft tube, allowing the incoming fresh air (through the oil fill) to flow through the valve chest and down into the crank case.
johnh7
Senior Member
My 38 pickup has a road draft tube on the oil pan. Does anyone have plans showing how they installed a PVC on the road draft tube? I already purchased a vented plate that installs under the carburetor. I will run a tube from the PCV to the vent in the plate. I should get good suction from there.
sidevalve8ba
Well-known member
This is the PCV routing that I came up with for my 8BA. I removed the crankcase vent pipe from the front of the intake. I then took an appropriate sized freeze and drilled an appropriate sized hole for the PCV valve grommet. I pressed this freeze plug grommet into the hole for the crankcase vent tube. The PCV valve is installed there and a smog hose run to the existing hole at the base of the rear carb on this Edelbrock intake. Seems to work fine for me.
The system breaths through the vented cap on the oil filler tube. I am always open for suggestions so if you see a way I can improve upon this system let me know.
The system breaths through the vented cap on the oil filler tube. I am always open for suggestions so if you see a way I can improve upon this system let me know.
Ross F-1
Well-known member
I had virtually the identical system on my truck for 5 years. Never any problem, until I installed an air/fuel monitor on the truck. I could see that to get it to idle, I had the mixture so rich it killed economy at cruise. If I'm not mistaken you also have a Ford 5.0 / 302 PCV, Fram #FV294? I switched to a Fram FV306, which is for a lot of Toyota engines. It provides enough PCV flow to work fine, but not so much as to upset the carb.
